Why reduced resources for building?

[DavidG]

I'm playing a PBW game and can't understand why some of my planets are constructed with reduced amounts. They are not on slow build. Some planets without a space yard and low pop are building with 2000 resources each as expected. However I've got some planets with shipyards that are only constructing with 1960 resources. Many others are at value much lower than I'm used to. So what gives? I did not create the race since I took over for another player but my Construction aptitude is average. Although since some of my planets are building at 2000 I assume there is another reason for the low build planets???